A flexible portable electronic device, such as that disclosed in EP Patent Application No 1158375A1 in the name of the Applicant, essentially includes a flexible body arranged to be capable of being secured to a part of a user's body, such as a wrist. At one location on the length of the flexible body there is arranged a cavity which houses an electronic assembly for elaborating information, a digital information display device for displaying the information elaborated by the electronic assembly, and an electrical power source for powering the electronic assembly.
The manufacture of this type of portable electronic device requires overmoulding the cavity using a polymer which is characterized by a high level of flexibility and resilience. Among the polymers suitable for this type of application, certain elastomers such as natural rubber, styrene-butadiene copolymer or thermoplastic polyurethane may be cited. Other flexible thermoplastic polymer type materials such as polyamide or silicone may also be envisaged. However, this overmoulding operation, whose purpose is to give the portable electronic device its final shape and thickness, has two notable drawbacks. First of all, certain materials such as elastomers are not sufficiently impermeable to protect the electronic components of the portable electronic device against humidity or against certain gases. Indeed, during the life of the portable electronic device, water vapour and gases slowly diffuse through the elastomer and can reach the electronic components, which is detrimental to the operation of said electronic components and may even eventually destroy them. The second drawback of the overmoulding operation lies in the high temperatures involved in overmoulding certain elastomers or plastic materials. These high temperatures are incompatible with the electronic components and would irreversibly damage said electronic components. The choice of materials that can be used for overmoulding the flexible portable electronic device is therefore limited by the implementation temperatures of these materials.